Aliphatic tertiary amines are important intermediate products in domestic and industrial application fields, and have been used in extensive applications such as, for example, fabric softeners, antistatic agents, additives for gasoline, shampoos, rinses, bactericides and detergents.
As the method for producing the aliphatic tertiary amines, there is known an amide reduction method in which an amide obtained from inexpensive regenerative fatty acids is used as a raw material. As the amide reduction method, there are conventionally known various methods using a cobalt-based catalyst, a noble metal-based catalyst, etc. However, any of these conventional methods inevitably require use of a solvent, resulting in problems such as poor productivity.
There is also known the method using a copper/chromium-based catalyst. For example, JP 3-500300A discloses a process for producing tertiary amines in which hydrogen and dimethylamine are flowed through and reacted with a raw amide under a pressure of from 1 to 10 MPa in a batch reactor charged with a copper/chromium/manganese catalyst. US 2006-287556A discloses a process for producing amines in which the reaction is conducted in the presence of hydrogen and an optional amine source under a pressure of from 0.2 to 5 MPa in a fixed bed reactor charged with a hydrogenation catalyst such as a copper/chromium catalyst. However, these catalysts used in the above conventional processes must be handled with great care to ensure a safety, etc., upon disposal. Therefore, there is a demand for chromium-free catalysts. Further, in these methods in which the amide compounds are reduced by flowing a mixed gas of hydrogen and the amine source (dimethylamine) therethrough, there are still present problems to be improved, such as a poor selectivity to the aimed tertiary amines in the method described in JP 3-500300A, and need of flowing a large excess amount of hydrogen through the raw amide in the method described in US 2006-287556A.
There is also disclosed a process for producing tertiary amines in which an amide compound is reduced in a hydrogen atmosphere using a chromium-free copper-based catalyst such as a copper/zinc catalyst, a copper/zinc/ruthenium catalyst and a copper/nickel/ruthenium catalyst (refer to JP 2001-302596A). However, the process is still unsatisfactory because of occurrence of a large amount of by-products such as alcohols.